In order to remove multipath interference, CP (Cyclic Prefix) is used in mobile communication systems based on the OFDM (Orthogonal Frequency Division Multiplexing) scheme and the DFT-Spread OFDM (Discrete Fourier Transform Spread OFDM) scheme, such as LTE (Long Term Evolution) scheme, WiFi (Wireless Fidelity) scheme, and WiMAX (Worldwide Interoperability for Microwave Access) scheme.
In such mobile communication system, CP with the same length is used for an uplink and a downlink based on an assumption that delay profiles of both links are substantially the same.